On 06.02.10 07:40, waggy wrote:
> I'm guessing the extra switching cost is more than offset by keeping
> the floating-point pipelines full.

Your guess is wrong as long as you counted "cores" as the logical number of 
cores seen by the operating system - including simultaneous multi-threading 
capabilities your processor may have.

What you are most likely seeing is that your OS gives your application 
slightly higher priority as a whole if it is running more threads, either 
because it is designed to detect compute-heavy applications or because its 
internal scheduling is on a thread rather than process basis.

	Thorsten

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